fix shared array terminology.

Shared arrays created by Array#dup and so on points
a shared_root object to manage lifetime of Array buffer.
However, sometimes shared_root is called only shared so
it is confusing. So I fixed these wording "shared" to "shared_root".

* RArray::heap::aux::shared -> RArray::heap::aux::shared_root
* ARY_SHARED() -> ARY_SHARED_ROOT()
* ARY_SHARED_NUM() -> ARY_SHARED_ROOT_REFCNT()

Also, add some debug_counters to count shared array objects.

* ary_shared_create: shared ary by Array#dup and so on.
* ary_shared: finished in shard.
* ary_shared_root_occupied: shared_root but has only 1 refcnt.
  The number (ary_shared - ary_shared_root_occupied) is meaningful.

1 files changed, 1 insertions, 1 deletions

diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index 863102228b..c7ce5ba3bd 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -1054,7 +1054,7 @@ struct RArray {
 	    long len;
 	    union {
 		long capa;
-		VALUE shared;
+		VALUE shared_root;
 	    } aux;
 	    const VALUE *ptr;
 	} heap;